A network is made up of a series of nodes interconnected by communication paths. Networks often interconnect computing devices of differing types and networks of various sizes. An enterprise network, for example, may interconnect with several local area networks (LANs) and one or more metropolitan area networks (MANs) or wide area networks (WANs).
In practice, many large networks with broad geographic coverage, like the public Internet, are made by connecting some of the nodes on one network with nodes of another network. This intermingling of network assets actually helps create the broader network.
A given network may be characterized by several factors like who can use the network, the type of traffic the network carries, the typical nature of the network's connections, and the transmission technology the network uses. For example, one network may be public and carry circuit switched voice traffic while another may be private and carry packet switched data traffic. Whatever the make-up, most networks facilitate the communication of information between at least two nodes, and as such act as communications networks.
A difficulty may arise, however, when a user of a network attempts to communicate with a user or an information source on another network. Communication across the boundaries of the two networks may create challenges. For example, internetworking calls may require the advanced scheduling of bridges. Internetworking calls may need to be placed via dedicated lines at an additional cost, and internetworking calls may create difficult compatibility issues if, for example, the networks involved use different protocols to provide service. Additionally, internetworking calls using packetized transmission technologies like Transmission Control Protocol and Internet Protocol (TCP/IP) may face quality of service (QoS) challenges.